The invention concerns an electric rotary machine, in particular a generator, with a stator and with a stator coil, which has a number of high-voltage cables. The invention also concerns a method for the cooling of such electric rotary machines.
Conventional electric rotary machines, for example, turbo-generators, are designed for a relatively low voltage of 10 . . . 25 kV. However, the rotary machine to which this invention refers is designed for high voltage. In this case, high voltage is understood to be the range from 30 kV to several 100 kV. Such a high-voltage generator is specially designed for the power supply of long-distance networks, for example, for 110 kV. The main advantage of the high-voltage generator is that it can feed power directly into the long-distance network, without needing a transformer.
An important difference between a conventional generator and the high-voltage generator consists in the design of its coil, in particular, its stator coil. In particular, this concerns the individual cables, which, in the case of high-voltage generators, are designed as high-voltage cables. Based on the clearly higher voltages, these high-voltage cables must have a fundamentally different insulation than the cables of conventional generators. The high-voltage cables are similar to conventional high-voltage cables and, as a rule, have a bundle of cable lanes, which are covered by an appropriate insulation, specifically plastic insulation.
Based on the distinctly higher voltages, high-voltage generators demand a different construction with regard to electric/magnetic boundary conditions as well as with regard to the required cooling.
A cooling system for such a high-voltage generator is known from WO 97/45914. The stator of this generator is layered by individual segment-forming sheets of metal in the longitudinal direction such that extending grooves are formed in the radial direction. Several high-voltage cables, which are arranged next to each other in the radial direction, run in each of the grooves. The groove has a complex geometry; i.e., its sidewalls are formed by a stringing together of curvatures corresponding to the individual high-voltage cables. Cooling channels that extend in the axial direction are provided between every two such grooves. The actual cooling cable, with a coolant flowing through it, is fed through the corresponding cooling channel. This arrangement requires an embedded material for the cooling cable, in order to achieve a good thermal contact between the cooling cable and the corresponding tooth-like stator segment.
The invention is based on the function of guaranteeing an efficient cooling for a high-voltage generator.
In accordance with the invention, this function is fulfilled by an electric rotary machine, in particular by a generator, with a stator and a stator coil, which has a number of high-voltage cables, whereby a coolant channel is provided, in which a number of the high-voltage cables are arranged.
An immediate cooling of the individual high-voltage cables is enabled by the arrangement of the high-voltage cables in the coolant channel. The heat is diverted directly by a coolant flowing through the coolant channel. Thus, there are no other components arranged between the coolant and the high-voltage cables that impair the thermal conductibility and thereby the cooling capacity.
The arrangement of the high-voltage cables in the coolant channel is thus comparable to the known state-of-the-art arrangement in a groove of the stator, with the important difference that, with the known generator, the high-voltage cables are cooled only indirectly. The groove is brought in as the coolant channel. The high-voltage cables thereby extend preferably in the axial or longitudinal direction of the generator and are arranged next to each other in the radial direction in the coolant channel.
For a simple construction of the stator, this is preferably separated into stator segments that form a circular ring as seen from the cross-section, whereby each stator segment has at least one coolant channel, in which several high-voltage cables are arranged. Through the arrangement of the coolant channels in each individual segment, an efficient and even cooling is realized.
The coolant channel is preferably designed as a cool gas channel; i.e., the cooling takes place, for example, via air or, in particular, with turbo-generators also via hydrogen. Compared to an oil-cooled generator, such a gas-cooled generator has advantages with respect to the coolant circulation method.
In order to achieve a particularly simple constructive arrangement, a preferred design form of the coolant channel has a rectangular cross-sectional geometry.
In order to effectively use the room available within the stator, the coolant channel extends outward preferably in the radial direction. In terms of a simple design, this take place in stages.
This advantageously enables, with the increasing width of the coolant channel, an increase in the number of high-voltage cables arranged next to each other in a direction perpendicular to the radial direction.
In accordance with the invention, this function is also fulfilled by a procedure for cooling an electric rotary machine, in particular, for cooling a generator, whereby the rotary machine has a stator with a stator winding, which comprises a number of high-voltage cables, and whereby the high-voltage cables are cooled immediately by a coolant.
This procedure advantageously uses the channel, in which the high-voltage cables run, as the guide for a coolant. An immediate, efficient, and even generator cooling is thus guaranteed.
The advantages mentioned with respect to the rotary machine and preferred design forms are present in the method in an analogous fashion.